A lot of people have the same question.
Check out this forum topic below for your answers
Basically, as long as the measurements are fairly close to their recommended 70cm x 45cm x 25cm you should be fine. If you have worries about it I would recommend giving topdeck a call They’re a pretty helpful bunch!
You probably won’t need to buy a new suitcase but even if you can’t use your own Jag suitcase, I’m sure there would be someone you know who would have a suitcase within those limits Even a friend of a friend. What you don’t have, you can always borrow…and therefore have more money for shopping Priorities are important! ;D lol
Hope that helps B-)